Modulation of intestinal cholesterol absorption by high glucose levels: impact on cholesterol transporters, regulatory enzymes, and transcription factors

Silicon as a Functional Meat Ingredient Improves Jejunal and Hepatic Cholesterol Homeostasis in a Late-Stage Type 2 Diabetes Mellitus Rat Model

Silicon included in a restructured meat (RM) matrix (Si-RM) as a functional ingredient has been demonstrated to be a potential bioactive antidiabetic compound. However, the jejunal and hepatic molecular mechanisms by which Si-RM exerts its cholesterol-lowering effects remain unclear. Male Wistar rats fed an RM included in a high-saturated-fat high-cholesterol diet (HSFHCD) combined with a low dose of streptozotocin plus nicotinamide injection were used as late-stage type 2 diabetes mellitus (T2DM) model. Si-RM was included into the HSFHCD as a functional food. An early-stage TD2M group fed a high-saturated-fat diet (HSFD) was taken as reference. Si-RM inhibited the hepatic and intestinal microsomal triglyceride transfer protein (MTP) reducing the apoB-containing lipoprotein assembly and cholesterol absorption. Upregulation of liver X receptor (LXRα/β) by Si-RM turned in a higher low-density lipoprotein receptor (LDLr) and ATP-binding cassette transporters (ABCG5/8, ABCA1) promoting jejunal cholesterol efflux and transintestinal cholesterol excretion (TICE), and facilitating partially reverse cholesterol transport (RCT). Si-RM decreased the jejunal absorptive area and improved mucosal barrier integrity. Consequently, plasma triglycerides and cholesterol levels decreased, as well as the formation of atherogenic lipoprotein particles. Si-RM mitigated the dyslipidemia associated with late-stage T2DM by Improving cholesterol homeostasis. Silicon could be used as an effective nutritional approach in diabetic dyslipidemia management.

Trimethylamine increases intestinal fatty acid absorption: in vitro studies in a Caco-2 cell culture system

Although elevated blood levels of trimethylamine N-oxide (TMAO) have been associated with atherosclerosis development in humans, the role of its gut microbiota-derived precursor, TMA, in this process has not been yet deciphered. Taking this into account, and the fact that increased intestinal fatty acid absorption contributes to atherosclerosis onset and progression, this study aimed to evaluate the effect of TMA on fatty acid absorption in a cell line that mimics human enterocytes. Caco-2 cells were treated with TMA 250 μM for 24 h. Fatty acid absorption was assessed by measuring the apical-to-basolateral transport and the intracellular levels of BODIPY-C12, a fluorescently labelled fatty acid analogue. Gene expression of the main intestinal fatty acid transporters was evaluated by real-time quantitative reverse transcription PCR. Compared to control conditions, TMA increased, in a time-dependent manner and by 20-50 %, the apical-to-basolateral transport and intracellular levels of BODIPY-C12 fatty acid in Caco-2 cells. Fatty acid transport protein 4 (FATP4) and fatty acid translocase (FAT)/CD36 gene expression were not stimulated by TMA, suggesting that TMA-induced increase in fatty acid transport may be mediated by an increase in FAT/CD36 and/or FATP4 activity and/or fatty acid passive transport. This study demonstrated that TMA increases the intestinal absorption of fatty acids. Future studies are necessary to confirm if this may constitute a novel mechanism that partially explains the existing positive association between the consumption of a diet rich in TMA sources (e.g. red meat) and the increased risk of atherosclerotic diseases.

Altered Distribution of Unesterified Cholesterol among Lipoprotein Subfractions of Patients with Diabetes Mellitus Type 2

Biomarkers are important tools to improve the early detection of patients at high risk for developing diabetes as well as the stratification of diabetic patients towards risks of complications. In addition to clinical variables, we analyzed 155 metabolic parameters in plasma samples of 51 healthy volunteers and 66 patients with diabetes using nuclear magnetic resonance (NMR) spectrometry. Upon elastic net analysis with lasso regression, we confirmed the independent associations of diabetes with branched-chain amino acids and lactate (both positive) as well as linoleic acid in plasma and HDL diameter (both inverse). In addition, we found the presence of diabetes independently associated with lower concentrations of free cholesterol in plasma but higher concentrations of free cholesterol in small HDL. Compared to plasmas of non-diabetic controls, plasmas of diabetic subjects contained lower absolute and relative concentrations of free cholesterol in all LDL and HDL subclasses except small HDL but higher absolute and relative concentrations of free cholesterol in all VLDL subclasses (except very small VLDL). These disbalances may reflect disturbances in the transfer of free cholesterol from VLDL to HDL during lipolysis and in the transfer of cell-derived cholesterol from small HDL via larger HDL to LDL.

Mechanism of the Regulation of Plasma Cholesterol Levels by PI(4,5)P2

Elevated low-density lipoprotein (LDL) cholesterol (LDLc) is one of the most well-established risk factors for cardiovascular disease, while high levels of high-density lipoprotein (HDL) cholesterol (HDLc) have been associated with protection from cardiovascular disease. Cardiovascular disease remains one of the leading causes of death worldwide; thus it is important to understand mechanisms that impact LDLc and HDLc metabolism. In this chapter, we will discuss molecular processes by which phosphatidylinositol-(4,5)-bisphosphate, PI(4,5)P₂, is thought to modulate LDLc or HDLc. Section 1 will provide an overview of cholesterol in the circulation, discussing processes that modulate the various forms of lipoproteins (LDL and HDL) carrying cholesterol. Section 2 will describe how a PI(4,5)P₂ phosphatase, transmembrane protein 55B (TMEM55B), impacts circulating LDLc levels through its ability to regulate lysosomal decay of the low-density lipoprotein receptor (LDLR), the primary receptor for hepatic LDL uptake. Section 3 will discuss how PI(4,5)P₂ interacts with apolipoprotein A-I (apoA1), the key apolipoprotein on HDL. In addition to direct mechanisms of PI(4,5)P₂ action on circulating cholesterol, Sect. 4 will review how PI(4,5)P₂ may indirectly impact LDLc and HDLc by affecting insulin action. Last, as cholesterol is controlled through intricate negative feedback loops, Sect. 5 will describe how PI(4,5)P₂ is regulated by cholesterol.

Comparison of apical and basolateral Cu treatment for iron-related gene regulation during deferoxamine induced iron deficiency

BACKGROUND

Intestinal copper transporter (Atp7a) mutant-brindled mice with systemic Cu deficiency had elevated Cu levels in enterocyte cells without any perturbation of iron-regulating genes, suggesting that blood Cu level might be important for intestinal iron homeostasis during iron deficiency (ID). We hypothesized that the blood Cu level and polarization (apical and basolateral) of enterocyte cells might be important regulators for the compensatory response on the regulation of genes in enterocyte cells during iron deficiency.

METHODS

We grew Caco-2 cells on a bicameral cell culture plate to mimic the human intestine system and on a regular tissue culture plate. Iron deficiency was induced by deferoxamine (DFO). The cells were treated with Cu and Cu with Fe following mRNA expressions of DMT1, FPN, TFR, and ANKRD37 were analyzed.

RESULTS

Our main finding was that basolateral treatment of Cu significantly reduced mRNA expressions of iron-regulated genes, including DMT1, FPN, TFR, and ANKRD37, compared to DFO-treated and DFO with apical Cu-treated groups in both bicameral and regular tissue culture plates.

CONCLUSIONS

Cu level in the basolateral side of Caco-2 cells significantly influenced the intracellular gene regulation in DFO-induced iron-deficient condition, and polarization of the cells might be important factor gene regulation in enterocyte cells.

Relationship between Diabetes Mellitus and Serum Lathosterol and Campesterol Levels: The CACHE Study DM Analysis

AIM

Risk of cardiovascular disease is increased in patients with diabetes mellitus (DM). Cholesterol metabolism (hepatic synthesis and intestinal absorption) is known to be associated with cardiovascular risk. Next, we examined the association of DM with cholesterol absorption/synthesis.

METHODS

The CACHE Consortium, which is comprised of 13 research groups in Japan possessing data of lathosterol (Latho, synthesis marker) and campesterol (Campe, absorption marker) measured by gas chromatography, compiled the clinical data using the REDCap system. Among the 3597 records, data from 2944 individuals were used for several analyses including this study.

RESULTS

This study analyzed data from eligible 2182 individuals including 830 patients with DM; 42.2% were female, median age was 59 years, and median HbA1c of patients with DM was 7.0%. There was no difference in Latho between DM and non-DM individuals. Campe and Campe/Latho ratio were significantly lower in DM individuals than in non-DM individuals. When the associations of glycemic control markers with these markers were analyzed with multivariable-adjusted regression model using restricted cubic splines, Campe and Campe/Latho ratio showed inverse associations with glucose levels and HbA1c. However, Latho showed an inverted U-shaped association with plasma glucose, whereas Latho showed a U-shaped association with HbA1c. These associations remained even after excluding statin and/or ezetimibe users.

CONCLUSION

We demonstrated that DM and hyperglycemia were independent factors for lower cholesterol absorption marker levels regardless of statin/ezetimibe use.

The Reciprocal Relationship between LDL Metabolism and Type 2 Diabetes Mellitus

Type 2 diabetes mellitus and insulin resistance feature substantial modifications of the lipoprotein profile, including a higher proportion of smaller and denser low-density lipoprotein (LDL) particles. In addition, qualitative changes occur in the composition and structure of LDL, including changes in electrophoretic mobility, enrichment of LDL with triglycerides and ceramides, prolonged retention of modified LDL in plasma, increased uptake by macrophages, and the formation of foam cells. These modifications affect LDL functions and favor an increased risk of cardiovascular disease in diabetic individuals. In this review, we discuss the main findings regarding the structural and functional changes in LDL particles in diabetes pathophysiology and therapeutic strategies targeting LDL in patients with diabetes.

Intestinal protection by proanthocyanidins involves anti-oxidative and anti-inflammatory actions in association with an improvement of insulin sensitivity, lipid and glucose homeostasis

Recent advances have added another dimension to the complexity of cardiometabolic disorders (CMD) by directly implicating the gastrointestinal tract as a key player. In fact, multiple factors could interfere with intestinal homeostasis and elicit extra-intestinal CMD. As oxidative stress (OxS), inflammation, insulin resistance and lipid abnormalities are among the most disruptive events, the aim of the present study is to explore whether proanthocyanidins (PACs) exert protective effects against these disorders. To this end, fully differentiated intestinal Caco-2/15 cells were pre-incubated with PACs with and without the pro-oxidant and pro-inflammatory iron/ascorbate (Fe/Asc). PACs significantly reduce malondialdehyde, a biomarker of lipid peroxidation, and raise antioxidant SOD2 and GPx via the increase of NRF2/Keap1 ratio. Likewise, PACs decrease the inflammatory agents TNFα and COX2 through abrogation of NF-κB. Moreover, according to crucial biomarkers, PACs result in lipid homeostasis improvement as reflected by enhanced fatty acid β-oxidation, diminished lipogenesis, and lowered gluconeogenesis as a result of PPARα, γ and SREBP1c modulation. Since these metabolic routes are mainly regulated by insulin sensitivity, we have examined the insulin signaling pathway and found an upregulation of phosphoPI3K/Akt and downregulation of p38-MAPK expressions, indicating beneficial effects in response to PACs. Taken together, PACs display the potential to counterbalance OxS and inflammation in Fe/Asc-exposed intestinal cells, in association with an improvement of insulin sensitivity, which ameliorates lipid and glucose homeostasis.

Glycomacropeptide Prevents Iron/Ascorbate-Induced Oxidative Stress, Inflammation and Insulin Sensitivity with an Impact on Lipoprotein Production in Intestinal Caco-2/15 Cells

Background. Metabolic Syndrome (MetS), a major worldwide concern for the public health system, refers to a cluster of key metabolic components, and represents a risk factor for diabetes and cardiovascular diseases. As oxidative stress (OxS) and inflammation are the major triggers of insulin sensitivity (IS), a cardinal MetS feature, the principal aim of the present work is to determine whether glycomacropeptide (GMP), a milk-derived bioactive peptide, exerts beneficial effects on their expression. Methods. Fully differentiated intestinal Caco-2/15 cells are used to evaluate the preventive action of 2 mg/mL GMP against OxS and inflammation induced by the mixture iron-ascorbate (Fe/Asc) (200 μM:2 mM). The potency of GMP of decreasing the production of lipoproteins, including chylomicrons (CM), very-low-density lipoproteins (VLDL) and low-density lipoproteins (LDL) is also assessed. Results. The administration of GMP significantly reduces malondialdehyde, a biomarker of lipid peroxidation, and raises superoxide dismutase 2 and glutathione peroxidase via the induction of the nuclear factor erythroid 2–related factor 2, a transcription factor, which orchestrates cellular antioxidant defenses. Similarly, GMP markedly lowers the inflammatory agents tumor necrosis factor-α and cyclooxygenase-2 via abrogation of the nuclear transcription factor-kB. Moreover, GMP-treated cells show a down-regulation of Fe/Asc-induced mitogen activated protein kinase pathway, suggesting greater IS. Finally, GMP decreases the production of CM, VLDL, and LDL. Conclusions. Our results highlight the effectiveness of GMP in attenuating OxS, inflammation and lipoprotein biogenesis, as well as improving IS, the key components of MetS. Further investigation is needed to elucidate the mechanisms mediating the preventive action of GMP.

Comparison of the Efficacy and Safety of Rosuvastatin/Ezetimibe Combination Therapy and Rosuvastatin Monotherapy on Lipoprotein in Patients With Type 2 Diabetes: Multicenter Randomized Controlled Study

INTRODUCTION

Ezetimibe/statin combination therapy has been reported to provide additional cardioprotective effects compared to statin monotherapy. The apolipoprotein B/A1 (apoB/A1) ratio is an effective predictor of cardiovascular diseases. The aim of this study was to compare the efficacy and safety of rosuvastatin/ezetimibe combination therapy versus rosuvastatin monotherapy using the apoB/A1 ratio in patients with diabetes and hypercholesterolemia.

METHODS

In this randomized, multicenter, open-label, parallel-group study, patients were randomly assigned to receive the combination therapy of rosuvastatin 5 mg/ezetimibe 10 mg once daily (n = 68) or monotherapy with rosuvastatin 10 mg once daily (n = 68), for 8 weeks.

RESULTS

After the 8-week treatment, percentage change (least-square means ± standard error) in the apoB/A1 ratio in the rosuvastatin/ezetimibe group was significantly decreased compared to the rosuvastatin group (- 46.14 ± 1.58% vs.  - 41.30 ± 1.58%, respectively; P = 0.03). In addition, the proportion of patients achieving > 50% reduction in low-density lipoprotein-cholesterol (LDL-C) and in the comprehensive lipid target (LDL-C < 70 mg/dL, non-HDL-cholesterol [non-HDL-C] < 100 mg/dL, and apoB < 80 mg/dL) was significantly different between the two groups (76.5 and 73.5% in the rosuvastatin/ezetimibe group and 47.1 and 45.6% in the rosuvastatin group, respectively; P < 0.001). The reduction in total cholesterol, non-HDL-C, LDL-C, and apoB were greater in the rosuvastatin/ezetimibe group than in the rosuvastatin group. Both treatments were well tolerated, and no between-group differences in drug-related adverse events were observed.

CONCLUSION

The apoB/A1 ratio was significantly reduced in patients receiving combination therapy with ezetimibe and rosuvastatin compared to those receiving rosuvastatin monotherapy. Both treatments were well tolerated in patients with type 2 diabetes and hypercholesterolemia.

TRIAL REGISTRATION

NCT03446261.

SR-BI as a target of natural products and its significance in cancer

Scavenger receptor class B type I (SR-BI) protein is an integral membrane glycoprotein. SR-BI is emerging as a multifunctional protein, which regulates autophagy, efferocytosis, cell survival and inflammation. It is well known that SR-BI plays a critical role in lipoprotein metabolism by mediating cholesteryl esters selective uptake and the bi-directional flux of free cholesterol. Recently, SR-BI has also been identified as a potential marker for cancer diagnosis, prognosis, or even a treatment target. Natural products are a promising source for the discovery of new drug leads. Multiple natural products were identified to regulate SR-BI protein expression. There are still a number of challenges in modulating SR-BI expression in cancer and in using natural products for modulation of such protein expression. In this review, our purpose is to discuss the relationship between SR-BI protein and cancer, and the molecular mechanisms regulating SR-BI expression, as well as to provide an overview of natural products that regulate SR-BI expression.

Regulation of autophagy and apoptosis by Dp44mT-mediated activation of AMPK in pancreatic cancer cells

Upon activation, the 5'-adenosine monophosphate-activated protein kinase (AMPK) increases catabolism, while inhibiting anabolism. The anti-cancer agent, di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone (Dp44mT), activates AMPK in multiple tumor cell-types (Biochim. Biophys Acta 2016;1863:2916-2933). This acts as an initial cell "rescue response" after iron-depletion mediated by Dp44mT. Considering Dp44mT-mediated AMPK activation, the role of AMPK on Dp44mT cytotoxicity was examined. Dp44mT increased the p-AMPK/AMPK ratio in multiple tumor cell-types over short (24 h) and longer (72 h) incubations. Notably, Dp44mT was more effective in inhibiting tumor cell proliferation after AMPK silencing, potentially due to the loss of AMPK-mediated metabolic plasticity that protects cells against Dp44mT cytotoxicity. The silencing of AMPK-increased cellular cholesterol and stabilized lysosomes against Dp44mT-mediated lysosomal membrane permeabilization. This was substantiated by studies demonstrating that the cholesterol-depleting agent, methyl-β-cyclodextrin (MβCD), restores Dp44mT-mediated lysosomal membrane permeabilization in AMPK silenced cells. The increased levels of cholesterol after AMPK silencing were independent of the ability of AMPK to inhibit the rate-limiting step of cholesterol synthesis via the inactivating phosphorylation of 3-hydroxy-3-methylglutaryl CoA reductase (HMGCR) at Ser872. In fact, Dp44mT did not increase phosphorylation of HMGCR at (Ser872), but decreased total HMGCR expression similarly in both the presence or absence of AMPK silencing. Dp44mT was demonstrated to increase autophagic initiation after AMPK silencing via an AMPK- and Beclin-1-independent mechanism. Further, there was increased cleaved caspase 3 and cleaved PARP after incubation of AMPK silenced cells with Dp44mT. Overall, AMPK silencing promotes Dp44mT anti-proliferative activity, suggesting a role for AMPK in rescuing its cytotoxicity by inhibiting autophagy and also apoptosis.

The Gastrointestinal Tract as Prime Site for Cardiometabolic Protection by Dietary Polyphenols

Substantial evidence from nutritional epidemiology links polyphenol-rich diets with reduced incidence of chronic disorders; however, biological mechanisms underlying polyphenol-disease relations remain enigmatic. Emerging evidence is beginning to unmask the contribution of the gastrointestinal tract on whole-body energy homeostasis, suggesting that the intestine may be a prime target for intervention and a fundamental site for the metabolic actions of polyphenols. During their transit through the gastrointestinal tract, polyphenols may activate enteric nutrient sensors ensuing appropriate responses from other peripheral organs to regulate metabolic homeostasis. Furthermore, polyphenols can modulate the absorption of glucose, attenuating exaggerated hormonal responses and metabolic imbalances. Polyphenols that escape absorption are metabolized by the gut microbiota and the resulting catabolites may act locally, activating nuclear receptors that control enteric functions such as intestinal permeability. Finally, polyphenols modulate gut microbial ecology, which can have profound effects on cardiometabolic health.

The Niemann-Pick C1-like 1 rs2073547 polymorphism is associated with type 2 diabetes mellitus in a Chinese population

Objective

To explore the association between Niemann–Pick C1-like 1 gene ( NPC1L1) single nucleotide polymorphisms and type 2 diabetes mellitus (T2DM) in a Chinese population.

Methods

Using propensity score matching, 490 T2DM patients and 490 matched controls were recruited from 13 communities in Guangxi, China. NPC1L1 rs217386 and rs2073547 genotyping was performed using a MassARRAY system.

Results

The rs2073547 genotype distribution differed significantly among patient groups. Low-density lipoprotein cholesterol levels were similar among different rs2073547 genotypes and alleles. The rs2073547 AG genotype was significantly more prevalent in patients with T2DM. After adjusting for risk or protective factors for diabetes, AG and GG+AG genotypes of rs2073547 were associated with significantly increased risks of T2DM. Compared with the AA genotype, the AG genotype was associated with a significantly higher risk of T2DM in participants with gamma-glutamyl transpeptidase (GGT) <45 U/L, systolic blood pressure (SBP) ≥140 mmHg, or triglyceride <1.70 mmol/L. In participants with GGT <45 U/L or SBP ≥140 mmHg, the GG+AG genotype was associated with a significantly higher T2DM risk versus the AA genotype.

Conclusions

The rs2073547 polymorphism of NPC1L1 may be related to T2DM susceptibility in the Chinese population.

Small Heterodimer Partner and Fibroblast Growth Factor 19 Inhibit Expression of NPC1L1 in Mouse Intestine and Cholesterol Absorption

BACKGROUND & AIMS

The nuclear receptor subfamily 0 group B member 2 (NR0B2, also called SHP) is expressed at high levels in the liver and intestine. Postprandial fibroblast growth factor 19 (human FGF19, mouse FGF15) signaling increases the transcriptional activity of SHP. We studied the functions of SHP and FGF19 in the intestines of mice, including their regulation of expression of the cholesterol transporter NPC1L1 )NPC1-like intracellular cholesterol transporter 1) and cholesterol absorption.

METHODS

We performed histologic and biochemical analyses of intestinal tissues from C57BL/6 and SHP-knockout mice and performed RNA-sequencing analyses to identify genes regulated by SHP. The effects of fasting and refeeding on intestinal expression of NPC1L1 were examined in C57BL/6, SHP-knockout, and FGF15-knockout mice. Mice were given FGF19 daily for 1 week; fractional cholesterol absorption, cholesterol and bile acid (BA) levels, and composition of BAs were measured. Intestinal organoids were generated from C57BL/6 and SHP-knockout mice, and cholesterol uptake was measured. Luciferase reporter assays were performed with HT29 cells.

RESULTS

We found that the genes that regulate lipid and ion transport in intestine, including NPC1L1, were up-regulated and that cholesterol absorption was increased in SHP-knockout mice compared with C57BL/6 mice. Expression of NPC1L1 was reduced in C57BL/6 mice after refeeding after fasting but not in SHP-knockout or FGF15-knockout mice. SHP-knockout mice had altered BA composition compared with C57BL/6 mice. FGF19 injection reduced expression of NPC1L1, decreased cholesterol absorption, and increased levels of hydrophilic BAs, including tauro-α- and -β-muricholic acids; these changes were not observed in SHP-knockout mice. SREBF2 (sterol regulatory element binding transcription factor 2), which regulates cholesterol, activated transcription of NPC1L1. FGF19 signaling led to phosphorylation of SHP, which inhibited SREBF2 activity.

CONCLUSIONS

Postprandial FGF19 and SHP inhibit SREBF2, which leads to repression of intestinal NPC1L1 expression and cholesterol absorption. Strategies to increase FGF19 signaling to activate SHP might be developed for treatment of hypercholesterolemia.

Insulin increases cholesterol uptake, lipid droplet content, and apolipoprotein B secretion in CaCo-2 cells by upregulating SR-BI via a PI3K, AKT, and mTOR-dependent pathway

The actions of insulin on intestinal cholesterol absorption and lipoprotein secretion are not well understood. Herein, we determined the effects of insulin on the levels of cholesterol transporter scavenger receptor, class B, type I (SR-BI), cellular cholesterol uptake, intracellular lipid accumulation, and lipoprotein secretion in a cellular model of human intestinal epithelium.

METHODS

CaCo-2 cells were cultured to postconfluency in Transwell filters and stimulated with glucose (25 mM) in the presence or absence of insulin (100 nM) at their basolateral surface. SR-BI mRNA and protein levels were quantified by quantitative reverse transcription-PCR and immunoblot, respectively. Polarized localization of SR-BI was determined by cell surface proteins biotinylation and streptavidin precipitation. Activities of PI3K, AKT, mTOR, and SR-BI were pharmacologically antagonized. Cholesterol uptake was assessed by NBD-cholesterol incorporation. Apolipoprotein (apo) B concentration was quantified by ELISA. Subcellular localization of neutral lipids (BODIPY) and SR-BI (immunofluorescence) was determined by confocal microscopy.

RESULTS

In polarized CaCo-2 cells, insulin increased SR-BI at the mRNA and protein levels. SR-BI was exclusively present at apical cell surface, as indicated by biotinylation and confocal microscopy analysis. Glucose did not modify SR-BI abundance or subcellular localization. Effects of insulin on SR-BI levels were abrogated by PI3K, AKT, or mTOR pharmacological antagonism. Cholesterol uptake, neutral lipid abundance, and apo B secretion were increased by insulin in CaCo-2 cells, and these effects were prevented by SR-BI pharmacological antagonism with block lipid transport-1.

CONCLUSIONS

insulin promotes cholesterol uptake, intracellular lipid store, and apo B-containing lipoproteins secretion by SR-BI-dependent mechanisms in a model of human intestinal epithelium.

A Newly Integrated Model for Intestinal Cholesterol Absorption and Efflux Reappraises How Plant Sterol Intake Reduces Circulating Cholesterol Levels

Cholesterol homeostasis is maintained through a balance of de novo synthesis, intestinal absorption, and excretion from the gut. The small intestine contributes to cholesterol homeostasis by absorbing and excreting it, the latter of which is referred to as trans-intestinal cholesterol efflux (TICE). Because the excretion efficiency of endogenous cholesterol is inversely associated with the development of atherosclerosis, TICE provides an attractive therapeutic target. Thus, elucidation of the mechanism is warranted. We have shown that intestinal cholesterol absorption and TICE are inversely correlated in intestinal perfusion experiments in mice. In this review, we summarized 28 paired data sets for absorption efficiency and fecal neutral sterol excretion, a surrogate marker of TICE, obtained from 13 available publications in a figure, demonstrating the inverse correlation were nearly consistent with the assumption. We then offer a bidirectional flux model that accommodates absorption and TICE occurring in the same segment. In this model, the brush border membrane (BBM) of intestinal epithelial cells stands as the dividing ridge for cholesterol fluxes, making the opposite fluxes competitive and being coordinated by shared BBM-localized transporters, ATP-binding cassette G5/G8 and Niemann-Pick C1-like 1. Furthermore, the idea is applied to address how excess plant sterol/stanol (PS) intake reduces circulating cholesterol level, because the mechanism is still unclear. We propose that unabsorbable PS repeatedly shuttles between the BBM and lumen and promotes concomitant cholesterol efflux. Additionally, PSs, which are chemically analogous to cholesterol, may disturb the trafficking machineries that transport cholesterol to the cell interior.

Differential association of ezetimibe-simvastatin combination with major adverse cardiovascular events in patients with or without diabetes: a retrospective propensity score-matched cohort study

Clinical trials suggested that the benefits of ezetimibe-statin combination therapy on major adverse cardiovascular events (MACE) might be greater in patients with diabetes. We aimed to investigate the differential association of ezetimibe-statin combination with incident MACE by presence of diabetes. In this retrospective cohort study, subjects treated with simvastatin 20 mg plus ezetimibe 10 mg (S + E) or simvastatin 20 mg alone (S) between 2005 and 2015 were 1:1 matched using propensity score as stratified by diabetes. Primary outcome was newly-developed MACE composed of cardiovascular death, ACS, coronary revascularization, or non-hemorrhagic stroke. During 5,077 and 12,439 person-years, the incidence rates of MACE were 24.9, 20.1, 35.3, and 22.8/1000 person-years among no diabetes S, no diabetes S + E, diabetes S, and diabetes S + E, respectively. Relative to no diabetes S, adjusted HR (aHR) for MACE in diabetes S was 1.23 (p = 0.086), whereas S + E was associated with a lower risk of MACE in both non-diabetic patients (aHR 0.76, p = 0.047) and diabetic patients (aHR 0.60, p = 0.007) with significant difference (relative excess risk due to interaction = -0.39, p = 0.044). In conclusion, reduction of MACE risk associated with ezetimibe plus simvastatin therapy relative to simvastatin alone was greater in patients with diabetes than in patients without diabetes.

Comparison of the Effects of Ezetimibe-Statin Combination Therapy on Major Adverse Cardiovascular Events in Patients with and without Diabetes: A Meta-Analysis

BACKGROUND

Ezetimibe-statin combination therapy has been found to reduce low density lipoprotein cholesterol levels and the risk of major adverse cardiovascular events (MACEs) in large trials. We sought to examine the differential effect of ezetimibe on MACEs when added to statins according to the presence of diabetes.

METHODS

Randomized clinical trials with a sample size of at least 50 participants and at least 24 weeks of follow-up that compared ezetimibe-statin combination therapy with a statin- or placebo-controlled arm and reported at least one MACE, stratified by diabetes status, were included in the meta-analysis and meta-regression.

RESULTS

A total of seven trials with 28,191 enrolled patients (mean age, 63.6 years; 75.1% men; 7,298 with diabetes [25.9%]; mean follow-up, 5 years) were analysed. MACEs stratified by diabetes were obtained from the published data (two trials) or through direct contact (five trials). No significant heterogeneity was observed among studies (I²=14.7%, P=0.293). Ezetimibe was associated with a greater reduction of MACE risk in subjects with diabetes than in those without diabetes (pooled relative risk, 0.84 vs. 0.93; P(heterogeneity)=0.012). In the meta-regression analysis, the presence of diabetes was associated with a greater reduction of MACE risk when ezetimibe was added to statins (β=0.87, P=0.038).

CONCLUSION

Ezetimibe-statin combination therapy was associated with greater cardiovascular benefits in patients with diabetes than in those without diabetes. Our findings suggest that ezetimibe-statin combination therapy might be a useful strategy in patients with diabetes at a residual risk of MACEs.

Correlation of CD81 and SCARB1 polymorphisms on virological responses in Iranian patients with chronic hepatitis C virus genotype 1

The cluster of differentiation 81 (CD81) and scavenger receptor class B member 1 (SCARB1) plays an important role in the entry of hepatitis C virus (HCV). We assessed the correlation of five single nucleotide polymorphisms (SNPs) of CD81 (rs800136, rs2651842, rs2522012, rs800146, and rs708564) and SCARB1 rs10846744 polymorphisms with treatment responses in 395 treatment-naïve patients with chronic HCV (CHC) genotype 1 treated with pegylated interferon-α and ribavirin (pegIFN-α/RBV). The frequency of rapid virologic response (RVR), complete early virologic response (cEVR) and sustained virologic response (SVR) were 57.2%, 55.2%, and 58.2%, respectively. RVR, cEVR, and SVR were significantly associated with CD81 rs800136 (CC), CD81 rs2651842 (AA), CD81 rs708564 (TT), and SCARB1 rs10846744 (CC). High rates of RVR, cEVR, and SVR were reported for the CD81 rs800136 (CC), CD81 rs2651842 (AA), and CD81 rs708564 (TT) genotypes when correlated with higher levels of low-density lipoprotein (LDL) and lower levels of high-density lipoprotein (HDL) as well as lower levels of HDL and LDL in the SCARB1 rs10846744 (CC) genotype. In addition, patients with GG genotype had higher fasting blood glucose (FBS) level than those with CC genotype. In conclusion, CD81 and SCARB1 SNPs may serve as powerful predictor factors for treatment responses in CHC patients, and this effect is correlated with serum lipoprotein and FBS levels.

Managing Dyslipidemia in Type 2 Diabetes

Cardiovascular disease is the most frequent cause of morbidity and mortality among individuals with diabetes and although there has been significant reduction in excess risk, these individuals remain at least twice as likely to sustain atherosclerotic events. Aggressive management of traditional factors, such as dyslipidemia, remains the cornerstone of risk mitigation. Diabetes and its associated insulin resistance generate qualitative and quantitative changes in lipid profile, which complicate effective treatment. This review summaries the background to diabetic dyslipidemia and provides a précis of the available management options.

Understanding Chylomicron Retention Disease Through Sar1b Gtpase Gene Disruption: Insight From Cell Culture

BACKGROUND

Understanding the specific mechanisms of rare autosomal disorders has greatly expanded insights into the complex processes regulating intestinal fat transport. Sar1B GTPase is one of the critical proteins governing chylomicron secretion by the small intestine, and its mutations lead to chylomicron retention disease, despite the presence of Sar1A paralog.

OBJECTIVE

The central aim of this work is to examine the cause-effect relationship between Sar1B expression and chylomicron output and to determine whether Sar1B is obligatory for normal high-density lipoprotein biogenesis.

APPROACH AND RESULTS

The SAR1B gene was totally silenced in Caco-2/15 cells using the zinc finger nuclease technique. SAR1B deletion resulted in significantly decreased secretion of triglycerides (≈40%), apolipoprotein B-48 (≈57%), and chylomicron (≈34.5%). The absence of expected chylomicron production collapse may be because of the compensatory SAR1A elevation observed in our experiments. Therefore, a double knockout of SAR1A and SAR1B was engineered in Caco-2/15 cells, which led to almost complete inhibition of triglycerides, apolipoprotein B-48, and chylomicron output. Further experiments with labeled cholesterol revealed the downregulation of high-density lipoprotein biogenesis in cells deficient in SAR1B or with the double knockout of the 2 SAR1 paralogs. Similarly, there was a fall in the movement of labeled cholesterol from cells to basolateral medium containing apolipoprotein A-I, thereby limiting newly synthesized high-density lipoprotein in genetically modified cells. The decreased cholesterol efflux was associated with impaired expression of ABCA1 (ATP-binding cassette subfamily A member 1).

CONCLUSIONS

These findings demonstrate that the deletion of the 2 SAR1 isoforms is required to fully eliminate the secretion of chylomicron in vitro. They also underscore the limited high-density lipoprotein production by the intestinal cells in response to SAR1 knockout.

High-Density Lipoproteins Rescue Diabetes-Impaired Angiogenesis via Scavenger Receptor Class B Type I

Disordered neovascularization and impaired wound healing are important contributors to diabetic vascular complications. We recently showed that high-density lipoproteins (HDLs) enhance ischemia-mediated neovascularization, and mounting evidence suggests HDL have antidiabetic properties. We therefore hypothesized that HDL rescue diabetes-impaired neovascularization. Streptozotocin-induced diabetic mice had reduced blood flow recovery and neovessel formation in a hindlimb ischemia model compared with nondiabetic mice. Reconstituted HDL (rHDL) infusions in diabetic mice restored blood flow recovery and capillary density to nondiabetic levels. Topical rHDL application rescued diabetes-impaired wound closure, wound angiogenesis, and capillary density. In vitro, rHDL increased key mediators involved in hypoxia-inducible factor-1α (HIF-1α) stabilization, including the phosphoinositide 3-kinase/Akt pathway, Siah1, and Siah2, and suppressed the prolyl hydroxylases (PHD) 2 and PHD3. rHDL rescued high glucose-induced impairment of tubulogenesis and vascular endothelial growth factor (VEGF) A protein production, a finding associated with enhanced phosphorylation of proangiogenic mediators VEGF receptor 2 and endothelial nitric oxide synthase. Siah1/2 small interfering RNA knockdown confirmed the importance of HIF-1α stability in mediating rHDL action. Lentiviral short hairpin RNA knockdown of scavenger receptor class B type I (SR-BI) in vitro and SR-BI(-/-) diabetic mice in vivo attenuated rHDL rescue of diabetes-impaired angiogenesis, indicating a key role for SR-BI. These findings provide a greater understanding of the vascular biological effects of HDL, with potential therapeutic implications for diabetic vascular complications.

Effect of fixed-dose combinations of ezetimibe plus rosuvastatin in patients with primary hypercholesterolemia: MRS-ROZE (Multicenter Randomized Study of ROsuvastatin and eZEtimibe)

AIM

We aimed to compare the effects of fixed-dose combinations of ezetimibe plus rosuvastatin to rosuvastatin alone in patients with primary hypercholesterolemia, including a subgroup analysis of patients with diabetes mellitus (DM) or metabolic syndrome (MetS).

METHOD

This multicenter eight-week randomized double-blind phase III study evaluated the safety and efficacy of fixed-dose combinations of ezetimibe 10 mg plus rosuvastatin, compared with rosuvastatin alone in patients with primary hypercholesterolemia. Four hundred and seven patients with primary hypercholesterolemia who required lipid-lowering treatment according to the ATP III guideline were randomized to one of the following six treatments for 8 weeks: fixed-dose combinations with ezetimibe 10 mg daily plus rosuvastatin (5, 10, or 20 mg daily) or rosuvastatin alone (5, 10, or 20 mg daily).

RESULTS

Fixed-dose combination of ezetimibe plus rosuvastatin significantly reduced LDL cholesterol, total cholesterol, and triglyceride levels compared with rosuvastatin alone. Depending on the rosuvastatin dose, these fixed-dose combinations of ezetimibe plus rosuvastatin provided LDL cholesterol, total cholesterol, and triglyceride reductions of 56%-63%, 37%-43%, and 19%-24%, respectively. Moreover, the effect of combination treatment on cholesterol levels was more pronounced in patients with DM or MetS than in non-DM or non-MetS patients, respectively, whereas the effect of rosuvastatin alone did not differ between DM vs non-DM or MetS vs non-MetS patients.

CONCLUSION

Fixed-dose combinations of ezetimibe and rosuvastatin provided significantly superior efficacy to rosuvastatin alone in lowering LDL cholesterol, total cholesterol, and triglyceride levels. Moreover, the reduction rate was greater in patients with DM or MetS.

Clinical outcome of statin plus ezetimibe versus high-intensity statin therapy in patients with acute myocardial infarction propensity-score matching analysis

BACKGROUND

It is unclear whether simvastatin-ezetimibe could be an alternative therapy to high-intensity statin therapy in high-risk patients. The aim of this study was to compare the clinical outcomes of simvastatin-ezetimibe and high-intensity statin therapy in patients with acute myocardial infarction (AMI), and especially in those with high-risk factor.

METHODS

A total of 3520 AMI patients in the KAMIR (Korea Acute Myocardial Infarction Registry) were classified into simvastatin-ezetimibe group (n=1249) and high-intensity statin group (n=2271). Multivariate analysis and propensity-score matching analysis were performed. The primary endpoint was major adverse cardiac events (MACE) at 12-months follow-up.

RESULTS

In overall AMI patients, MACE occurred in 116 patients (9.3%) in simvastatin-ezetimibe group and 116 patients (5.1%) in high-intensity statin group. The difference in MACE between groups was driven by repeat revascularization (5.9% vs. 2.2%). After propensity matching analysis, simvastatin-ezetimibe was associated with a higher incidence of MACE than high-intensity statin therapy (adjusted hazard ratio: 3.090, 95% confidence interval: 1.715 to 5.566, p<0.001). However, in patients with high-risk factors, such as diabetes, old age, or heart failure, simvastatin-ezetimibe had similar incidence of MACE compared with high-intensity statin therapy in further adjusted analysis.

CONCLUSIONS

In overall AMI patients, high-intensity statin therapy had better clinical outcomes than simvastatin-ezetimibe. However, in patients with high-risk factor, simvastatin-ezetimibe had comparable clinical outcomes to high-intensity statin therapy. Therefore, simvastatin-ezetimibe could be used as an alternative to high-intensity statin therapy in such patients.

Association of SCARB1 Gene Polymorphisms with Virological Response in Chronic Hepatitis C Patients Receiving Pegylated Interferon plus Ribavirin Therapy

The scavenger receptor type B class I(SR-BI) is a receptor for high-density lipoproteins(HDL) and one of entry factors for hepatitis C virus(HCV). We examined the association of single nucleotide polymorphisms(SNPs) of the SCARB1 gene, which encodes SR-BI, with virologic responses to pegylated interferon-based treatment in Asian chronic hepatitis C(CHC) patients. Human genomic and clinical data were collected from 156 consecutive Taiwanese HCV genotype 1 or 2 patients who received pegylated interferon plus ribavirin therapy and 153 non-HCV healthy subjects. Three SNPs(rs10846744, rs5888, and rs3782287) of the SCARB1 gene that have been linked to humans diseases were investigated. rs10846744 rather than rs5888 or rs3782287 was associated with serum HCV RNA level and sustained virologic response(SVR) to pegylated interferon plus ribavirin therapy in CHC patients(GG vs. non-GG genotype, Adjusted Odds Ratio, 95% CI: 0.32, 0.11–0.95, P = 0.039). Among patients with IL28B rs8099917 non-TT genotypes, those with rs10846744 non-GG genotype had a higher SVR rate than those with GG genotypes. In addition, patients with GG genotype had a higher fasting blood glucose level than those with CC genotype. In conclusion, SCARB1 gene polymorphisms may serve as a potential predictor of treatment responses in CHC patients receiving interferon-based therapy. (ClinicalTrials.gov number, NCT02714712).

Intravenous Glucose Acutely Stimulates Intestinal Lipoprotein Secretion in Healthy Humans

OBJECTIVE

Increased production of intestinal triglyceride-rich lipoproteins (TRLs) contributes to dyslipidemia and increased risk of atherosclerotic cardiovascular disease in insulin resistance and type 2 diabetes. We have previously demonstrated that enteral glucose enhances lipid-stimulated intestinal lipoprotein particle secretion. Here, we assessed whether glucose delivered systemically by intravenous infusion also enhances intestinal lipoprotein particle secretion in humans.

APPROACH AND RESULTS

On 2 occasions, 4 to 6 weeks apart and in random order, 10 healthy men received a constant 15-hour intravenous infusion of either 20% glucose to induce hyperglycemia or normal saline as control. Production of TRL-apolipoprotein B48 (apoB48, primary outcomes) and apoB100 (secondary outcomes) was assessed during hourly liquid-mixed macronutrient formula ingestion with stable isotope enrichment and multicompartmental modeling, under pancreatic clamp conditions to limit perturbations in pancreatic hormones (insulin and glucagon) and growth hormone. Compared with saline infusion, glucose infusion induced both hyperglycemia and hyperinsulinemia, increased plasma triglyceride levels, and increased TRL-apoB48 concentration and production rate (P<0.05), without affecting TRL-apoB48 fractional catabolic rate. No significant effect of hyperglycemia on TRL-apoB100 concentration and kinetic parameters was observed.

CONCLUSIONS

Short-term intravenous infusion of glucose stimulates intestinal lipoprotein production. Hyperglycemia may contribute to intestinal lipoprotein overproduction in type 2 diabetes.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT02607839.

Ezetimibe/statin combination therapy to treat patients with type 2 diabetes

Patients with diabetes represent a population at higher risk for cardiovascular disease. Diabetic dyslipidemia is characterized by the so-called atherogenic lipid triad, consisting of an increase in small dense low density lipoprotein particles and in triglyceride-rich lipoproteins, and a decrease in high-density lipoprotein cholesterol, with an increase in non-HDL cholesterol. Numerous trials have investigated the efficacy of add-on ezetimibe therapy for patients with type 2 diabetes and not controlled by statin therapy. The published data highly suggest that patients with type 2 diabetes may be more likely to benefit from ezetimibe/statin combination therapy. However, evidence specifically addressing hard clinical endpoints and prospective trials addressing differences in response between patients with or without diabetes are still needed.

Dyslipidaemia of diabetes and the intestine

Atherosclerosis is the major complication of diabetes and has become a major issue in the provision of medical care. In particular the economic burden is growing at an alarming rate in parallel with the increasing world-wide prevalence of diabetes. The major disturbance of lipid metabolism in diabetes relates to the effect of insulin on fat metabolism. Raised triglycerides being the hallmark of uncontrolled diabetes, i.e., in the presence of hyperglycaemia. The explosion of type 2 diabetes has generated increasing interest on the aetiology of atherosclerosis in diabetic patients. The importance of the atherogenic properties of triglyceride rich lipoproteins has only recently been recognised by the majority of diabetologists and cardiologists even though experimental evidence has been strong for many years. In the post-prandial phase 50% of triglyceride rich lipoproteins come from chylomicrons produced in the intestine. Recent evidence has secured the chylomicron as a major player in the atherogenic process. In diabetes chylomicron production is increased through disturbance in cholesterol absorption, in particular Neimann Pick C1-like1 activity is increased as is intestinal synthesis of cholesterol through 3-hydroxy-3-methyl glutaryl co enzyme A reductase. ATP binding cassette proteins G5 and G8 which regulate cholesterol in the intestine is reduced leading to chylomicronaemia. The chylomicron particle itself is atherogenic but the increase in the triglyceride-rich lipoproteins lead to an atherogenic low density lipoprotein and low high density lipoprotein. The various steps in the absorption process and the disturbance in chylomicron synthesis are discussed.

Prevention of oxidative stress, inflammation and mitochondrial dysfunction in the intestine by different cranberry phenolic fractions

Cranberry fruit has been reported to have high antioxidant effectiveness that is potentially linked to its richness in diversified polyphenolic content. The aim of the present study was to determine the role of cranberry polyphenolic fractions in oxidative stress (OxS), inflammation and mitochondrial functions using intestinal Caco-2/15 cells. The combination of HPLC and UltraPerformance LC®-tandem quadrupole (UPLC-TQD) techniques allowed us to characterize the profile of low, medium and high molecular mass polyphenolic compounds in cranberry extracts. The medium molecular mass fraction was enriched with flavonoids and procyanidin dimers whereas procyanidin oligomers (DP > 4) were the dominant class of polyphenols in the high molecular mass fraction. Pre-incubation of Caco-2/15 cells with these cranberry extracts prevented iron/ascorbate-mediated lipid peroxidation and counteracted lipopolysaccharide-mediated inflammation as evidenced by the decrease in pro-inflammatory cytokines (TNF-α and interleukin-6), cyclo-oxygenase-2 and prostaglandin E2. Cranberry polyphenols (CP) fractions limited both nuclear factor κB activation and Nrf2 down-regulation. Consistently, cranberry procyanidins alleviated OxS-dependent mitochondrial dysfunctions as shown by the rise in ATP production and the up-regulation of Bcl-2, as well as the decline of protein expression of cytochrome c and apoptotic-inducing factor. These mitochondrial effects were associated with a significant stimulation of peroxisome-proliferator-activated receptor γ co-activator-1-α, a central inducing factor of mitochondrial biogenesis and transcriptional co-activator of numerous downstream mediators. Finally, cranberry procyanidins forestalled the effect of iron/ascorbate on the protein expression of mitochondrial transcription factors (mtTFA, mtTFB1, mtTFB2). Our findings provide evidence for the capacity of CP to reduce intestinal OxS and inflammation while improving mitochondrial dysfunction.

Dietary carbohydrates and intestinal lipoprotein production

PURPOSE OF REVIEW

To review new evidence that dietary monosaccharides enhance intestinal chylomicron secretion.

RECENT FINDINGS

There is abundant evidence linking diets that are high in carbohydrate content with hypertriglyceridemia. In addition, epidemiological studies reveal that the increase in dietary sugars and refined carbohydrates are associated with the rising prevalence of the metabolic syndrome and type 2 diabetes. Association studies, however, cannot prove causation. Mechanistic studies to date have focused on the link between carbohydrate ingestion and hepatic very low-density lipoprotein metabolism, with very little appreciation that dietary carbohydrates may also regulate intestinal lipid absorption and chylomicron secretion. We have recently studied this phenomenon in healthy humans and have shown that both glucose and fructose, infused concomitantly with a lipid emulsion directly into the duodenum and under conditions of a pancreatic clamp, stimulate chylomicron particle secretion. There are a paucity of data regarding the cellular and molecular mechanisms of this effect, which remains largely unknown and a matter of speculation.

SUMMARY

Sugar in the diet enhances dietary fat absorption and chylomicron secretion. Whether this phenomenon contributes quantitatively to the well described hypertriglyceridemia that occurs with diets high in carbohydrate and low in fat requires further investigation, as does the underlying cellular mechanism. A thorough understanding of this phenomenon could provide useful information to optimize dietary guidelines.

Effects of ezetimibe/simvastatin 10/20 mg vs. atorvastatin 20 mg on apolipoprotein B/apolipoprotein A1 in Korean patients with type 2 diabetes mellitus: results of a randomized controlled trial

BACKGROUND

Although the efficacy of ezetimibe/simvastatin and atorvastatin on traditional lipid parameters has been studied extensively, the apolipoprotein B/apolipoprotein A1 (ApoB/ApoA1) ratio, which has a better predictive value for cardiovascular events, has not previously been used as a primary endpoint in these two treatment groups.

OBJECTIVE

Our objective was to compare the efficacy and safety of ezetimibe/simvastatin 10/20 mg versus atorvastatin 20 mg once daily in Korean patients with type 2 diabetes mellitus.

STUDY DESIGN

This study was an open-label, randomized, controlled study. Type 2 diabetes patients with high levels of low-density lipoprotein (LDL) cholesterol (>100 mg/dL) were randomized to receive ezetimibe/simvastatin or atorvastatin.

MAIN OUTCOME MEASURE

The primary endpoint was the difference in the percent change of ApoB/ApoA1 at 12 weeks, and secondary endpoints were changes in lipid profiles, glycosylated hemoglobin (HbA1c), homeostatic model assessment (HOMA) index, and C-reactive protein.

RESULTS

In total, 132 patients (66 for each group) were enrolled and randomized. After 12 weeks of treatment, the ApoB/ApoA1 ratio was significantly reduced in both groups; however, the difference of changes between the two groups was not statistically significant (ezetimibe/simvastatin -38.6 ± 18.0 % vs. atorvastatin -34.4 ± 15.5 %; p = 0.059). There were no significant differences in changes to total cholesterol, LDL cholesterol, high-density lipoprotein cholesterol, triglycerides, ApoB, and ApoB48 between the two groups. However, the increments of ApoA1 were significantly greater in the ezetimibe/simvastatin group than in the atorvastatin group (2.8 ± 10.0 vs. -1.8 ± 9.8 %; p = 0.002). In the per-protocol analysis, improvement in ApoB/ApoA1 was significantly greater in the ezetimibe/simvastatin group (-42.8 ± 11.8 vs. -36.7 ± 13.2 %; p = 0.019). The changes in HbA1c, HOMA index, and C-reactive protein were comparable between the two groups. The adverse reaction rate was similar between the two groups (24.2 vs. 34.9 %; p = 0.180).

CONCLUSION

Ezetimibe/simvastatin 10/20 mg is comparable to atorvastatin 20 mg for the management of dyslipidemia, and may have more favorable effects on apolipoprotein profiles than atorvastatin 20 mg in Korean patients with type 2 diabetes mellitus.

Efficacy of combination of Ezetimibe 10 mg and rosuvastatin 2.5 mg versus rosuvastatin 5 mg monotherapy for hypercholesterolemia in patients with type 2 diabetes

BACKGROUND

Statins are used to treat hypercholesterolemia in patients with type 2 diabetes mellitus, but many of these patients fail to achieve the target LDL-C level. Recent reports have suggested that a synergistic effect can be obtained by concomitant administration of the cholesterol absorption inhibitor ezetimibe and a statin. However, in patients with type 2 diabetes who are already being treated with satins, it remains unclear whether it is more effective to add ezetimibe or to increase the statin dose. Therefore, this study was performed to examine the effects of these two regimens on LDL-C and lipoproteins.

METHODS

The subjects were type 2 diabetic patients under treatment with rosuvastatin (2.5 mg daily), who had LDL-C levels ≥80 mg/dL. They were randomly allocated to a group that received add-on therapy with ezetimibe at 10 mg/day (combination group, n = 40) or an increase of the rosuvastatin dose to 5 mg/day (dose escalation group, n = 39). These two groups were compared at baseline and after 12 weeks of treatment.

RESULTS

The percent change of LDL-C was -31% in the combination group and -12% in the dose escalation group. Both groups showed a significant decrease, but the decrease was greater in the combination group. In both groups, there was a significant decrease in the levels of small dense LDL-C, oxidized LDL and remnant-like lipoprotein cholesterol. For all of these parameters, the percent changes were greater in the combination group. Only the combination group showed a significant decrease of triglycerides. Multivariate analysis was performed to identify factors associated with reaching an LDL-C level <80 mg/dL. As a result, add-on therapy with ezetimibe was extracted as a factor related to improvement of LDL-C.

CONCLUSIONS

Compared with increasing the dose of rosuvastatin, the combination of rosuvastatin and ezetimibe not only achieves quantitative but also qualitative improvement of serum lipid levels in type 2 diabetic patients, suggesting that this combination could suppress the progression of atherosclerosis.

TRIAL REGISTRATION

UMIN000011005.

EXPERT CONSENSUS. ROLE OF COMBINATION LIPID-LOWERING THERAPY (SIMVASTATIN/EZETIMIBE 20/10 MG) IN THE CORRECTION OF LIPID METABOLISM DISTURBANCES IN PATIENTS WITH CHRONIC KIDNEY DISEASE

Expert Consensus. Role of combination lipid-lowering therapy (simvastatin/ezetimibe 20/10 mg) in the correction of lipid metabolism disturbances in patients with chronic kidney disease.

Role of the apical and basolateral domains of the enterocyte in the regulation of cholesterol transport by a high glucose concentration

We have recently shown that a high glucose (HG) concentration raised intestinal cholesterol (CHOL) transport and metabolism in intestinal epithelial cells. The objective of the present work is to determine whether the stimulus for increased CHOL absorption by glucose originates from the apical site (corresponding to the intestinal lumen) or from the basolateral site (related to blood circulation). We tackled this issue by using differentiated Caco-2/15 cells. Only basolateral medium, supplemented with 25 mmol/L glucose, stimulated [(14)C]-CHOL uptake via the up-regulation of the critical CHOL transporter NPC1L1 protein, as confirmed by its specific ezetimibe inhibitor that abolished the rise in glucose-mediated CHOL capture. No significant changes were noted in SR-BI and CD36. Elevated CHOL uptake was associated with an increase in the transcription factors SREBP-2, LXR-β, and ChREBP, along with a fall in RXR-α. Interestingly, although the HG concentration in the apical medium caused modest changes in CHOL processing, its impact was synergetic with that of the basolateral medium. Our results suggest that HG concentration influences positively intestinal CHOL uptake when present in the basolateral medium. In addition, excessive consumption of diets containing high levels of carbohydrates may strengthen intestinal CHOL uptake in metabolic syndrome, thereby contributing to elevated levels of circulating CHOL and, consequently, the risk of developing type 2 diabetes and cardiovascular disease.

Evidence of sugar sensitive genes in the gut of a carnivorous fish species

The ability of intestine to sense glucose in carnivorous animals (consuming minimal carbohydrate) has been partially evaluated to date only in cats. We have evaluated the expression of markers involved in the detection of simple sugars in the intestine of the strict carnivorous fish species rainbow trout (Oncorhynchus mykiss) in response to an oral glucose load and to glucose, galactose and mannose stimulation in vitro. These markers include metabolic (GLUT2 and glucokinase (hexokinase IV, GK)) and electrogenic (SGLT1) sensors, the nuclear receptor nr1h3 and the components of the G-protein-coupled taste receptors (tas1r2-like, tas1r3-like and gnat3-like). For the first time, we show that the gut of rainbow trout can detect simple sugars including glucose, galactose and mannose and respond by changing the expression levels of glucose-sensing proteins. The glucosensing response based on the metabolic and nuclear receptor systems had not been evidenced before in any carnivorous vertebrate species, whereas the responses of markers of the electrogenic mechanism and the taste receptor mechanism were different than those already described in cats. When the responses observed in rainbow trout were compared with those of omnivorous mammals, similar responses were obtained for nr1h3 whereas several differences arise in the responses of the other markers. Intestinal glucose sensing in the rainbow trout appears to be distinct from that reported for other carnivores such as cats and omnivores, revealing a novel glucose sensing mechanism not related entirely to diet in vertebrates and supports the idea that this species constitute a robust model for nutrient sensing study. Since only mRNA abundance is presented, depth studies are needed to fully understand the importance of the present findings.

The role of the gut in reverse cholesterol transport--focus on the enterocyte

In the arterial intima, macrophages become cholesterol-enriched foam cells and atherosclerotic lesions are generated. This atherogenic process can be attenuated, prevented, or even reversed by HDL particles capable of initiating a multistep pathway known as the macrophage-specific reverse cholesterol transport. The macrophage-derived cholesterol released to HDL is taken up by the liver, secreted into the bile, and ultimately excreted in the feces. Importantly, the absorptive epithelial cells lining the lumen of the small intestine, the enterocytes, express several membrane-associated proteins which mediate the influx of luminal cholesterol and its subsequent efflux at their apical and basolateral sides. Moreover, generation of intestinal HDL and systemic effects of the gut microbiota recently revealed a direct link between the gut and the cholesterol cargo of peripheral macrophages. This review summarizes experimental evidence establishing that the reverse cholesterol transport pathway which initiates in macrophages is susceptible to modulation in the small intestine. We also describe four paths which govern cholesterol passage across the enterocyte and define a role for the gut in the regulation of reverse cholesterol transport. Understanding the concerted function of these paths may be useful when designing therapeutic strategies aimed at removing cholesterol from the foam cells which occupy atherosclerotic lesions.

D-Glucose modulates intestinal Niemann-Pick C1-like 1 (NPC1L1) gene expression via transcriptional regulation

The expression of intestinal Niemann-Pick C1-like 1 (NPC1L1) cholesterol transporter has been shown to be elevated in patients with diseases associated with hypercholesterolemia such as diabetes mellitus. High levels of glucose were shown to directly increase the expression of NPC1L1 in intestinal epithelial cells, but the underlying mechanisms are not fully defined. The present studies were, therefore, undertaken to examine the transcriptional regulation of NPC1L1 expression in human intestinal Caco2 cells in response to glucose. Removal of glucose from the culture medium of Caco2 cells for 24 h significantly decreased the NPC1L1 mRNA, protein expression, as well as the promoter activity. Glucose replenishment significantly increased the promoter activity of NPC1L1 in a dose-dependent manner compared with control cells. Exposure of Caco2 cells to nonmetabolizable form of glucose, 3-O-methyl-d-glucopyranose (OMG) had no effect on NPC1L1 promoter activity, indicating that the observed effects are dependent on glucose metabolism. Furthermore, glucose-mediated increase in promoter activity was abrogated in the presence of okadaic acid, suggesting the involvement of protein phosphatases. Glucose effects on several deletion constructs of NPC1L1 promoter demonstrated that cis elements mediating the effects of glucose are located in the region between -291 and +56 of NPC1L1 promoter. Consistent with the effects of glucose removal on NPC1L1 expression in Caco2 cells, 24-h fasting resulted in a significant decrease in the relative expression of NPC1L1 in mouse jejunum. In conclusion, glucose appears to directly modulate NPC1L1 expression via transcriptional mechanisms and the involvement of phosphatase-dependent pathways.

Virulence meets metabolism: Cra and KdpE gene regulation in enterohemorrhagic Escherichia coli

Gastrointestinal (GI) bacteria sense diverse environmental signals as cues for differential gene regulation and niche adaptation. Pathogens such as enterohemorrhagic Escherichia coli (EHEC), which causes bloody diarrhea, use these signals for the temporal and energy-efficient regulation of their virulence factors. One of the main virulence strategies employed by EHEC is the formation of attaching and effacing (AE) lesions on enterocytes. Most of the genes necessary for the formation of these lesions are grouped within a pathogenicity island, the locus of enterocyte effacement (LEE), whose expression requires the LEE-encoded regulator Ler. Here we show that growth of EHEC in glycolytic environments inhibits the expression of ler and consequently all other LEE genes. Conversely, growth within a gluconeogenic environment activates expression of these genes. This sugar-dependent regulation is achieved through two transcription factors: KdpE and Cra. Both Cra and KdpE directly bind to the ler promoter, and Cra’s affinity to this promoter is catabolite dependent. Moreover, we show that the Cra and KdpE proteins interact in vitro and that KdpE’s ability to bind DNA is enhanced by the presence of Cra. Cra is important for AE lesion formation, and KdpE contributes to this Cra-dependent regulation. The deletion of cra and kdpE resulted in the ablation of AE lesions. One of the many challenges that bacteria face within the GI tract is to successfully compete for carbon sources. Linking carbon metabolism to the precise coordination of virulence expression is a key step in the adaptation of pathogens to the GI environment.

An appropriate and prompt response to environmental cues is crucial for bacterial survival. Cra and KdpE are two proteins found in both nonpathogenic and pathogenic bacteria that regulate genes in response to differences in metabolite concentration. In this work, we show that, in the deadly pathogen enterohemorrhagic Escherichia coli (EHEC) O157:H7, which causes bloody diarrhea, these two proteins influence important virulence traits. We also propose that their control of one or more of these virulence traits is due to the direct interaction of the Cra and KdpE proteins with each other, as well as with their DNA targets. This work shows how EHEC coopts established mechanisms for sensing the metabolites and stress cues in the environment, to induce virulence factors in a temporal and energy-efficient manner, culminating in disease. Understanding how pathogens commandeer nonpathogenic systems can help us develop measures to control them.

Modulatory role of PYY in transport and metabolism of cholesterol in intestinal epithelial cells

Background

Gastrointestinal peptides are involved in modulating appetite. Other biological functions attributed to them include the regulation of lipid homeostasis. However, data concerning PYY remain fragmentary. The objectives of the study were: (i) To determine the effect of PYY on intestinal transport and synthesis of cholesterol, the biogenesis of apolipoproteins (apos) and assembly of lipoproteins and (ii) To analyze whether the effects of PYY are similar according to whether cells are exposed to PYY on apical or basolateral surface.

Methodology/Principal Findings

Caco-2/15 cells were incubated with PYY (1–36) administered either to the apical or basolateral medium, at concentrations of 50 or 200 nM for 24 hours. De novo synthesis of cholesterol, cholesterol uptake, and assembly of lipoproteins were evaluated through the incorporation of [¹⁴C]-acetate, [¹⁴C]-cholesterol, and [¹⁴C]-oleate, respectively. Biogenesis of apos (A-I, A-IV, E, B-48 and B-100) was examined by the incorporation of [³⁵S]-methionine. The influence of PYY on protein and mRNA levels of many key mediators of lipid metabolism was analyzed by Western blot and PCR, respectively. Our results show that PYY influenced cholesterol metabolism in Caco-2/15 cells depending on the site of PYY delivery. Apical addition of PYY significantly lowered the incorporation of [¹⁴C]-cholesterol likely via the reduction of NPC1L1, stimulated intracellular cholesterol synthesis probably through an increase in SREBP-2 expression, whereas it concomitantly increased apo A-I synthesis and decreased LDL secretion. In contrast, basolateral PYY reduced the production of chylomicrons (CM) as well as the biogenesis of apos B-48 and B-100, while lowering the expression of the transcription factors RXRα and PPAR(α,β).

Conclusions/Significance

PYY is capable of influencing cholesterol homeostasis in intestinal Caco-2/15 cells depending on the site delivery. Apical PYY was able to decrease cholesterol uptake via NPC1L1 downregulation, whereas basolateral PYY diminished CM output through the biogenesis decline of apos B-48 and B-100.

Recent advances in small bowel diseases: Part II

As is the case in all areas of gastroenterology and hepatology, in 2009 and 2010 there were many advances in our knowledge and understanding of small intestinal diseases. Over 1000 publications were reviewed, and the important advances in basic science as well as clinical applications were considered. In Part II we review six topics: absorption, short bowel syndrome, smooth muscle function and intestinal motility, tumors, diagnostic imaging, and cystic fibrosis.

Tissue cholesterol content alterations in streptozotocin-induced diabetic rats

AIM

Diabetes is associated with elevated serum total cholesterol level and disrupted lipoprotein subfractions. The aim of this study was to examine alterations in the tissue cholesterol contents closely related to diabetic complications.

METHODS

Intraperitoneal injection of streptozotocin was used to induce type 1 diabetes in adult male Sprague-Dawley rats. On d 35 after the injection, liver, heart, intestine, kidney, pancreas, cerebral cortex and hippocampus were isolated from the rats. The content of total and free cholesterol in the tissues was determined using HPLC. The ATP-binding cassette protein A1 (ABCA1) protein and ApoE mRNA were measured using Western blot and QT-PCR analyses, respectively.

RESULTS

In diabetic rats, the level of free cholesterol was significantly decreased in the peripheral tissues, but significantly elevated in hippocampus, as compared with those in the control rats. Diabetic rats showed a trend of decreasing the total cholesterol level in the peripheral tissues, but significant change was only found in kidney and liver. In diabetic rats, the level of the ABCA1 protein was significantly increased in the peripheral tissues and cerebral cortex; the expression of ApoE mRNA was slightly decreased in hippocampus and cerebral cortex, but the change had no statistical significance.

CONCLUSION

Type 1 diabetes decreases the free cholesterol content in the peripheral tissues and increases the free cholesterol content in hippocampus. The decreased free cholesterol level in the peripheral tissues may be partly due to the increased expression of the ABCA1 protein.

Inhibition of fatty acid translocase cluster determinant 36 (CD36), stimulated by hyperglycemia, prevents glucotoxicity in INS-1 cells

The purpose of the present study was to determine whether exposure of pancreatic islets to glucotoxic conditions changes fatty acid translocase cluster determinant 36 (CD36) and examine the role of CD36 on the induction of glucotoxicity. We measured the changes of CD36 and insulin secretion in high glucose (30 mM) exposed INS-1 cells and CD36 suppressed INS-1 cells by transfection of CD36 siRNA. The intracellular peroxide level of INS-1 cells increased in the high glucose media compared to normal glucose (5.6mM) media. The mRNA levels of insulin and PDX-1, as well as glucose stimulated insulin secretion (GSIS) were decreased in INS-1 cells exposed to high glucose media compared to normal glucose media, while CD36 and palmitate uptake were significantly elevated with exposure to high glucose media for 12h. The inhibition of CD36 reversed the decreased GSIS and intracellular peroxide level in INS-1 cells. These results suggest that high glucose may exacerbate glucotoxicity via increasing fatty acid influx by elevation of CD36 expression, and that CD36 may be a possible target molecule for preventing glucotoxicity in pancreatic beta-cells.

Lipid-altering efficacy and safety profile of combination therapy with ezetimibe/statin vs. statin monotherapy in patients with and without diabetes: an analysis of pooled data from 27 clinical trials

AIM

This post hoc analysis compared the lipid-altering efficacy and safety of ezetimibe 10 mg plus statin (EZE/statin) vs. statin monotherapy in hypercholesterolaemic patients with and without diabetes.

METHODS

A pooled analysis of 27 previously published, randomized, double-blind, active- or placebo-controlled clinical trials comprising 21 794 adult patients with (n = 6541) and without (n = 15253) diabetes receiving EZE/statin or statin alone for 4-24 weeks evaluated percentage change from baseline in lipids and other parameters. Consistency of the treatment effect across the subgroups was tested using treatment × subgroup interaction. No multiplicity adjustments were made.

RESULTS

Treatment effects within both subgroups were generally consistent with the overall population. EZE/statin was more effective than statin alone in improving low-density lipoprotein cholesterol (LDL-C), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), triglycerides (TGs), non-HDL-C, apolipoprotein (apo) B and high-sensitivity C-reactive protein (hs-CRP) in the overall population and both subgroups. Patients with diabetes achieved significantly larger reductions in LDL-C, TC and non-HDL-C compared with non-diabetic patients. Incidences of adverse events or creatine kinase elevations were similar between groups. A small but significantly higher incidence of alanine aminotransferase or aspartate aminotransferase elevations was seen in patients receiving EZE/statin (0.6%) vs. statin monotherapy (0.3%) in the overall population.

CONCLUSIONS

Treatment with EZE/statin vs. statin monotherapy provided significantly larger reductions in LDL-C, TC, TG, non-HDL-C, apo B and hs-CRP and significantly greater increases in HDL-C, with a similar safety profile in patients with and without diabetes. Reductions in LDL-C, TC and non-HDL-C were larger in patients with diabetes than in patients without diabetes.

Scavenger receptor class B member 1 protein: hepatic regulation and its effects on lipids, reverse cholesterol transport, and atherosclerosis

Scavenger receptor class B member 1 (SR-BI, also known as SCARB1) is the primary receptor for the selective uptake of cholesterol from high-density lipoprotein (HDL). SR-BI is present in several key tissues; however, its presence and function in the liver is deemed the most relevant for protection against atherosclerosis. Cholesterol is transferred from HDL via SR-BI to the liver, which ultimately results in the excretion of cholesterol via bile and feces in what is known as the reverse cholesterol transport pathway. Much of our knowledge of SR-BI hepatic function and regulation is derived from mouse models and in vitro characterization. Multiple independent regulatory mechanisms of SR-BI have been discovered that operate at the transcriptional and post-transcriptional levels. In this review we summarize the critical discoveries relating to hepatic SR-BI cholesterol metabolism, atherosclerosis, and regulation of SR-BI, as well as alternative functions that may indirectly affect atherosclerosis.

Oxidative stress and mitochondrial functions in the intestinal Caco-2/15 cell line

Background

Although mitochondrial dysfunction and oxidative stress are central mechanisms in various pathological conditions, they have not been extensively studied in the gastrointestinal tract, which is known to be constantly exposed to luminal oxidants from ingested foods. Key among these is the simultaneous consumption of iron salts and ascorbic acid, which can cause oxidative damage to biomolecules.

Methodology/Principal Findings

The objective of the present work was to evaluate how iron-ascorbate (FE/ASC)-mediated lipid peroxidation affects mitochondrion functioning in Caco-2/15 cells. Our results show that treatment of Caco-2/15 cells with FE/ASC (0.2 mM/2 mM) (1) increased malondialdehyde levels assessed by HPLC; (2) reduced ATP production noted by luminescence assay; (3) provoked dysregulation of mitochondrial calcium homeostasis as evidenced by confocal fluorescence microscopy; (4) upregulated the protein expression of cytochrome C and apoptotic inducing factor, indicating exaggerated apoptosis; (5) affected mitochondrial respiratory chain complexes I, II, III and IV; (6) elicited mtDNA lesions as illustrated by the raised levels of 8-OHdG; (7) lowered DNA glycosylase, one of the first lines of defense against 8-OHdG mutagenicity; and (8) altered the gene expression and protein mass of mitochondrial transcription factors (mtTFA, mtTFB1, mtTFB2) without any effects on RNA Polymerase. The presence of the powerful antioxidant BHT (50 µM) prevented the occurrence of oxidative stress and most of the mitochondrial abnormalities.

Conclusions/Significance

Collectively, our findings indicate that acute exposure of Caco-2/15 cells to FE/ASC-catalyzed peroxidation produces harmful effects on mitochondrial functions and DNA integrity, which are abrogated by the powerful exogenous BHT antioxidant. Functional derangements of mitochondria may have implications in oxidative stress-related disorders such as inflammatory bowel diseases.